1. Field of the Invention
The present invention relates to a reset driving method of an alternating current plasma display panel (hereinafter, PDP) having four electrode, in particular, to a novel driving method for AC PDP and AC PDP using the driving method, in which the driving method of a four electrodes surface discharge alternating current plasma display panel (hereinafter, four electrodes surface discharge AC PDP) where an auxiliary electrode is inserted between a scan electrode and a sustain electrode of a three electrodes surface discharge alternating current plasma display panel of the related art (hereinafter, a three electrode surface discharge AC PDP) is improved, thereby, a stable reset discharge can be generated by lowering the reset voltage, and a stable address operation can be performed.
2. Description of the Related Art
FIG. 1 is a drawing illustrating an example of the configuration of a discharge cell of three electrode surface discharge AC PDP.
As shown in FIG. 1, a scan electrode 23 and a sustain electrode 27 which are covered with a dielectric layer 19 and a protection layer 17 on a front glass substrate are disposed in parallel to form a pair.
An address electrode 10 which is covered with a dielectric layer 13 exists on a rear glass substrate, while a barrier rib 15 is formed in parallel with the address electrode 10. A phosphor is disposed on the surface of the dielectric layer 13 and both sides of the barrier rib 15.
The front substrate 30 and the rear substrate 20 are coalesced in order that the scan electrode 23 and the sustain electrode 27 intersects with the address electrode 10. Thereby, a discharge space can be secured between the barrier ribs, so that the discharge space which is disposed in the intersection of the address electrode 10, the scan electrode 23 and the sustain electrode 27 forms a discharge cell.
FIG. 2 is a drawing illustrating a subfield driving method which is one of the driving methods for AC PDP of the related art.
In the AC PDP, an image is divided into a plurality of subfields to display a gray scale. FIG. 2 illustrates the control of 28 gray scales. The ratio of the light emitting period of each subfield is set to be 1, 2, 4, 8, 16, 32, 64, 128. Accordingly, the gray scale can be displayed by the combination of the light emitting of each subfield.
Further, the operation in one subfield will be described. One subfield includes a reset period, an address period, and a sustain period. In an initialization period (reset period), the wall charges of a discharge cell where a sustain discharge is generated and a discharge cell where a sustain discharge is not generated is set to be uniform.
In the address period, a discharge cell is selected so as to perform a sustain discharge by performing a selective write or erase discharge. In the sustain period, in the cell selected in the address period, voltages are alternately applied to the scan electrode and the sustain electrode to perform a sustain discharge.
FIG. 3A is a drawing illustrating waveforms for driving in a three electrode surface discharge AC PDP. FIG. 3B is a drawing illustrating the change of the distribution of the wall charges in the reset period corresponding to the waveform (hereinafter, ‘a first case’).
Referring to FIG. 3A and FIG. 3B, the ADS (Addressing and Display Separated) subfield reset method in the three electrodes surface discharge AC PDP is described.
First, as to the wall charges and an application pulse in the erase period (1), after the application of the last pulse of the sustain discharge, positive charges are accumulated in the sustain electrode X, while negative charges are accumulated in the scan electrode Y and a lot of positive charges are accumulated in the address electrode A.
Immediately after the sustain discharge, the erase pulse of a ramp waveform is applied to the sustain electrode X so as to erase the wall charges which are formed after the sustain discharge, thereby, the wall charges are gradually erased due to the erase pulse (FIG. 3B (1)).
Second, as to the wall charges and an application pulse in the ramp-up period (2), a voltage of a ramp waveform which is higher than the firing voltage of the sustain electrode X and the scan electrode Y is applied to the scan electrode Y such that a weak reset discharge is generated in all discharges cells from the scan electrode Y to the sustain electrode X and the address electrode A.
Accordingly, negative charges are accumulated in the scan electrode Y, while positive charges are accumulated in the sustain electrode x and the address electrode A (FIG. 3B (2)).
Third, as to the wall charges and an application pulse in the ramp-down period (3), a ramp waveform having a gentle slope which is opposite to the slope in the ramp-up period is applied to the scan electrode Y, while the positive voltage is applied to the sustain electrode X such that a weak reset discharge is generated in all discharges cells.
Accordingly, the wall charges formed in the ramp-up period, that is, the wall charges (−) in the scan electrode Y and the wall charges (+) in the sustain electrode X are decreased, while the wall charges in the address electrode A is optimized for address operation in the next address period (FIG. 3B (3)).
When the driving waveform of the related art is used for forming wall charges suitable for the address operation by sufficiently accumulating a lot of (+) wall charges in the address electrode A and (−) wall charges in the scan electrode, the voltage of approximately 400V is required in case of AC PDP having 60 μm˜80 μm gap of the sustain electrode X.
As described, since the efficiency of the three electrode AC PDP is low, the power consumption is high in case of the full screen light emitting, therefore, there is a problem in that the efficiency should be enhanced so as to lower the power consumption.
Accordingly, recently, the long gap discharge where the gap between the scan electrode and the sustain electrode is long is used. Hereinafter, the change of the distribution of the wall charges in the reset period due to the long gap discharge will be described.
FIG. 3C is a drawing illustrating the change of the distribution of the wall charges in the reset period in case, without an auxiliary electrode, the waveforms of the related art is applied to AC PDP having the coplanar gap (the gap between the scan electrode and the sustain electrode) of 200 μm (hereinafter, “a second case”).
The erase pulse is applied to the sustain electrode X in the erase period (1), so that a little of (−) wall charges are accumulated in the scan electrode Y, while a little of (+) wall charges are accumulated in the address electrode A.
A rising voltage is applied to the scan electrode Y in the ramp up period (2), thereby, a discharge is generated between each electrodes. Accordingly, a lot of (−) wall charges are accumulated in the scan electrode Y, while the corresponding (+) wall charges are accumulated in the sustain electrode X and the address electrode A.
In addition, a falling voltage is applied to the scan electrode Y in the ramp down period (3), thereby, the wall charges which are accumulated in each electrodes can be erased.
However, in this case, as to the discharge between the scan electrode Y and the address electrode A, due to the long gap (the extension of the coplanar gap), the gap between the scan electrode Y and the address electrode A becomes relatively shorter than the gap between the sustain electrode X and the address electrode A, thereby, the discharge is more actively generated.
In result, the quantity of the wall charges which are accumulated in the address electrode A in of the erase period becomes smaller than the quantity of the wall charges in FIG. 3B.
In addition to the long gap electrode structure, for a high efficiency characteristic, with broadening the gap between the scan electrode Y and the sustain electrode X, a four electrode AC PDP where an auxiliary electrode is inserted between the scan electrode Y and the sustain electrode X has been suggested.
However, when AC PDP having the four electrode configuration is used with the driving method of the related art, the reset voltage is increased and the address discharge becomes unstable, thereby, there is a problem in that a stable operation can not be performed.